About guitars I use VSTi 'Sytrus' with FL Studio. Sytrus has a lot of guitar presets, and others. But all presets sound synthetic^^
I use many VSTi for 8 bit sounds : 3x Osc for "chip-vocals" ; and Peach, Toad, Bleep for others.
By the way, the "chip-vocals" are the purpose of Cérès;, a synthetiser who ""sings"" (clean and scream, it is the same VST). However, I must improve this concept.